This invention relates to a water jet propulsion unit and more particularly to an improved watercraft construction and a propulsion unit therefor and to an improved arrangement for assisting the steering of a watercraft powered by a jet propulsion unit.
The advantages of jet propulsion units for watercraft are well known. Generally, these units permit the operation of the watercraft in shallower water than more conventional propeller driven craft. In addition, the use of jet propulsion units has a number of other advantages in that they provide a neat configuration for the watercraft and storage of the watercraft both in the water and out of the water can be facilitated. However, as with conventional watercraft, there are some disadvantages that are existent with jet propelled watercraft.
For example, when the watercraft is left in the water for a long period of time and not utilized, encrustation of elements such as barnacles in the running components of the propulsion unit can be a problem. In one form of jet propulsion unit, an outboard motor type of jet propulsion unit is employed that employs rather than a propeller a jet propulsion unit for achieving watercraft propulsion. Of course, this type of propulsion unit can easily be tilted up out of the water as can the associated stern drive jet propulsion units in which the jet propulsion unit is mounted on the stern of a watercraft as with conventional propeller driven inboard/outboard drives. However, the use of such outboard motor type jet propulsion units has the disadvantages common with outboard motors. That is, they provide an unsightly appearance for the watercraft, they raise the center of gravity and tend to concentrate a large portion of the weight at the hull of the watercraft and have other disadvantages.
Therefore, it is more desirable if the jet propulsion unit can be mounted in a tunnel formed at the rear of the watercraft hull. This provides not only a neat assembly, but also gives rise to improved construction of the watercraft as a whole by lowering its center of gravity and by moving heavy masses more forward in the hull. When the jet propulsion unit is positioned in or beneath the hull, many of the problems as aforenoted will be encountered. That is, the jet propulsion unit will clearly be underwater at all times even when not in use and encrustation can occur. Furthermore, because of its nature and the fact that the jet propulsion unit permits operating in shallow water, it may at times become clogged with foreign materials such as seaweed, sand or the like. When positioned in the tunnel of the watercraft hull, however, servicing is more difficult.
It is, therefore, a principal object of this invention to provide an improved watercraft and jet propulsion unit therefor.
It is a further object of this invention to provide a jet propulsion unit for a watercraft wherein the jet propulsion unit is positioned within the hull of the watercraft but nevertheless can be drained of water even when the watercraft is in the body of water but when it is not being operated.
It is a further object of this invention to provide an improved arrangement which permits the trim adjustment of a jet propulsion unit of this type.
It is yet a further object of this invention to provide a watercraft and hull arrangement having a jet propulsion unit that is positioned within a tunnel and wherein the jet propulsion unit can be conveniently serviced without necessitating removal from the hull or removal of the hull from the body of water in which the watercraft is operating.
It is known that the steering of a jet propelled watercraft is usually achieved by steering of the discharge nozzle of the jet propulsion unit. This means that the steering is somewhat related to the speed at which water is passing through the jet propulsion unit. Although this is generally acceptable, there are times when the steering by the jet propulsion unit alone may not be adequate. For example, when travelling at slow speeds or coasting, the jet propulsion unit itself may not provide adequate steering.
It has, therefore, been proposed to employ a separate rudder which can also be used for steering purposes when the jet propulsion unit steering is not fully effective. However, such rudders can become damaged, particularly when considering the type of shallow water in which jet propelled boats can be operated.
It is, therefore, a still further object of this invention to provide an improved steering rudder arrangement for a jet propulsion unit wherein the steering rudder will be protected from damage if underwater obstacles are encountered.